http://www.thlib.org/collections/texts/ ... ermano/b6/"Thus The Seventeen Tantras are most likely an extraction and canonization of a selection of Tantras out of a broader movement, which Zhangtön Trashi Dorjé identified as the Unsurpassed Secret Cycle to differentiate it out from earlier precedents, and presumably to distinguish himself from other redactors/codifiers of this broader movement."